1. Field of the Invention
This invention relates in general to the mining of minerals from underwater and in particular to the harvesting of mineral nodules located on the floor of an ocean.
2. L Description of the Prior Art
Ferromanganese nodules or aggregates are known to exist in large quantities on ocean floors, frequently at depths varying from 5,000 to 19,000 feet. Previously, means have been suggested for scraping or picking up the loose aggregates from the sea floor and transmitting them to the surface. U.S. Pat. No. 3,588,174 discloses a collector that is towed across the undersea floor, dislodging the aggregates partially by water spray, the aggregates being pumped to the surface in a stream of water within a conduit. U.S. Pat. No. 3,802,740 and Canadian Pat. No. 692,998 disclose devices that also collect aggregates from an undersea floor and transmit them in a conduit to the surface. Such devices convey the collected aggregate to the surface by utilizing submerged pumps. A submerged pump usually requires a protective capsule and may be difficult to service, especially at great depths.
It is known to use dual concentric pipes for well drilling, as shown in U.S. Pat. No. 1,461,240, where water is pumped down the annulus, then returned up the inner pipe to create a suction to draw loose material from the floor. This eduction system cannot be used with the high hydrostatic pressure that occurs at depths of 5,000 to 19,000 feet. Dual concentric pipes are also known in well drilling using gas as a circulation medium, as in U.S. Pat. No. 3,065,807.